1. Field of the Invention
The present invention relates to an internal combustion engine having a cylinder formed with a water jacket and a vehicle provided with the same.
2. Description of the Related Art
In an engine in which a cylinder and a cylinder head are combined, the cylinder is exposed to high-temperature combustion gas in the same manner as the cylinder head. Conventionally, water-cooled type engines having a cylinder are frequently provided with a water jacket.
In recent years, the use of a cylinder made of aluminum alloy instead of a cylinder made of cast iron has been proposed in order to make an engine lightweight. Aluminum alloy is superior in thermal conductivity to iron. Therefore, a water jacket having the same shape and dimension as those in a conventional cylinder made of cast iron is conventionally provided in a cylinder made of aluminum alloy on the basis that sufficient cooling can be obtained with the same water jacket. See, for example, Abstract of Pamphlet of International Publication WO2002/053899.
The inventors of the present application have found that when using a material having an excellent thermal conductivity as a material for a cylinder, an overall desired performance for an internal combustion engine cannot necessarily be obtained with the same water jacket as a conventional cast iron cylinder.